Demands for globally environmental protection have been increased in recent years. High efficiency, in particular, has been strongly required in a refrigerator and other refrigeration cycle devices.
In the prior art, a sealed compressor of this type is exemplified by using a suction muffler made of a resin (see, for example, Patent Document 1). Hereinafter, the above-described sealed compressor in the prior art will be explained with reference to the drawings.
FIG. 3 is a vertical cross-sectional view showing a sealed compressor in the prior art disclosed in Patent Document 1; and FIG. 4 is a vertical cross-sectional view showing a suction muffler in the sealed compressor.
With reference to FIGS. 3 and 4, at a bottom of sealed container 1, oil 3 is reserved and refrigerant 5 is filled. Compressor body 7 is resiliently supported with respect to sealed container 1 via suspension spring 9.
Compressor body 7 is provided with electromotive component 11 and compressive component 13 disposed above electromotive component 11. Electromotive component 11 includes stator 15 and rotor 17.
Compressive component 13 is provided with crankshaft 23, block 29, piston 31, valve plate 33, suction valve 37, and connector 39. Here, crankshaft 23 includes eccentric shaft 19 and main shaft 21. Block 29 is formed integrally with cylinder 27 defining compression chamber 25. Connector 39 is adapted to connect eccentric shaft 19 and piston 31 to each other. Suction valve 37 is designed to open or close suction port 35, which is formed in valve plate 33 for sealing an end face of cylinder 27.
Main shaft 21 of crankshaft 23 is rotatably pivoted on bearing 41 of block 29. Moreover, to main shaft 21 is fixed rotor 17. Furthermore, crankshaft 23 is equipped with oil supply mechanism 43 including a spiral groove formed on main shaft 21, and the like.
Additionally, valve plate 33 attached to the end face of cylinder 27 and cylinder head 45 for closing valve plate 33 securely hold suction muffler 47 therebetween.
Suction muffler 47 is molded of a resin such as PBT (i.e., polybutylene terephthalate). Suction muffler 47 includes muffler body 51, inlet tube 53, and outlet tube 55, and further, is provided with oil drain port 57 at a lower end of muffler body 51. Here, muffler body 51 defines muffler space 49. Muffler space 49 communicates with a space defined inside of sealed container 1 via inlet tube 53. In addition, muffler space 49 communicates with compression chamber 25 via outlet tube 55.
Outlet tube 55 includes bent portion 59, first outlet tube portion 61, and second outlet tube portion 63. First outlet tube portion 61 and second outlet tube portion 63 are continuous to each other at a right angle. Here, bent portion 59 is obtained by bending a tube in the middle between an opening exposed to muffler space 49 and an opening formed in a vicinity of suction valve 37. First outlet tube portion 61 extends from bent portion 59 toward muffler space 49. Second outlet tube portion 63 extends from bent portion 59 toward suction valve 37.
A description will be given below of the operation of the sealed compressor such configured as described above in the prior art disclosed in Patent Document 1.
First, a current flows in stator 15, thereby generating a magnetic field in the sealed compressor. Crankshaft 23 is rotated by rotating rotor 17 fixed to main shaft 21, so that piston 31 makes a reciprocal motion inside of cylinder 27 via connector 39 rotatably fixed to eccentric shaft 19.
The reciprocal motion of piston 31 allows refrigerant 5 to be repeatedly sucked to compression chamber 25, compressed therein, and discharged to a refrigeration cycle, not shown.
In a suction stroke, refrigerant 5 which has been returned from the refrigeration cycle is introduced into compression chamber 25 from suction muffler 47 through suction port 35 communicating with compression chamber 25 by opening or closing suction valve 37.
Here, suction muffler 47 reduces noise generated by intermittent suction of refrigerant 5, and further, prevents refrigerant 5 passing through suction muffler 47 from being heated since it is made of a resin having a small thermal conductivity.
Since bent portion 59 is formed in outlet tube 55, a height of suction muffler 47 can be reduced, and therefore, suction muffler 47 can be used in a sealed compressor having a small height.
On the other hand, oil supply mechanism 43 carries oil 3 from the bottom of sealed container 1 to compressive component 13 by utilizing a centrifugal force or the like generated by the rotation of crankshaft 23.
Carried oil 3 lubricates crankshaft 23 and a slide portion such as bearing 41, and then, spatters inside of sealed container 1 from an upper end of crankshaft 23, so as to lubricate piston 31, cylinder 27, and the like. Thereafter, spattering oil 3 adheres to sealed container 1, and then, flows down to the bottom along an inner wall of sealed container 1. In the meantime, heat is transmitted from oil 3 to sealed container 1, to then radiate from sealed container 1 to an outside, thus cooling the sealed compressor.
Moreover, oil 3 spattering inside of sealed container 1 is sucked also into suction muffler 47 together with refrigerant 5. Oil 3 sucked together with refrigerant 5 is separated from refrigerant 5 when refrigerant 5 released from inlet tube 53 into muffler space 49 is reduced in flow rate. Most of separated oil 3 resides at the bottom of muffler body 51, and then, is drained outside of suction muffler 47 through oil drain port 57.
However, with the configuration in the prior art, a part of oil 3 spattering inside of muffler space 49 cannot fall but adheres onto the inner wall of muffler space 49 or an outer surface of outlet tube 55. In particular, oil 3 adhering to the outer surface of outlet tube 55 is urged by a flow of refrigerant 5 flowing from inlet tube 53, to be moved toward the opening exposed to muffler space 49 in first outlet tube portion 61, and further, oil droplets are formed during the movement. The droplets of oil 3 are urged by the flow of refrigerant 5, and thus, are moved along the inner wall of outlet tube 55, as indicated by arrows in FIG. 4, thereby raising a possibility that oil 3 flows into compression chamber 25 in a large amount.
If oil 3 flows into compression chamber 25 in a large amount, an increased load during compression may increase an input or inhibit refrigerant 5 from being sufficiently compressed, resulting in degraded refrigeratory efficiency. Worse still, abrupt fluctuations in compressive load may induce generation of noise.
Alternatively, if oil 3 flows into the refrigeration cycle in a large amount, a heat exchanger may be degraded.